Trimming the grass around their homes may be a chore for many humans, but for Brandt’s voles it’s a matter of life and death, new research shows. The little rodents are found in grasslands in Mongolia, Russia—and China, where they’re regularly observed trimming tall grasses near the openings of their burrows so they can watch the skies for predators such as shrikes, their chief avian adversary.

When shrikes are flying around, Brandt’s voles use their teeth to fell the bunchgrass dotting their home fields. But the rodents neither eat the plant nor bring it into their burrows, scientists observed. As a test, the scientists put nets over the voles’ burrows so shrikes couldn’t get close—and the voles